Data is generally encrypted to prevent access by unauthorized individuals. Typically, the data is encrypted using a key. In order for the encrypted data to be read, it must be unencrypted using the key. Thus, for example, if a laptop is stolen, data stored on its hard drive cannot be accessed by a perpetrator unless the key is used. To delete encrypted data typically all of the data is rewritten with 1s and 0s, which is typically repeated a number of times.